In what will eventually be a boost for Potomac River water quality and the Bay cleanup, the EPA has proposed strict new limits for the region’s largest wastewater treatment plant that could slash millions of pounds of nitrogen pollution annually.

The agency—after reviewing comments by environmental groups—in December proposed capping nitrogen discharges from the massive Blue Plains wastewater treatment plant, which handles sewage from more than 2.1 million customers in the District of Columbia and parts of Maryland and Virginia.

The cost of the upgrade is expected to be between $500 million and $1 billion and would be split among municipalities discharging to the plant.

Right now, the amount of nitrogen discharged from the plant typically ranges from 6 million to 8.5 million pounds a year—by far the largest single nitrogen discharger in the Bay watershed. When the upgrade is completed, that will be slashed to less than 4.7 million pounds a year.

That would be a significant step toward meeting nitrogen reduction goals aimed at cleaning up the river, and the Chesapeake. As of 2005, the river needed an additional 16.6 million pounds of nitrogen reductions to meet its river goal of 35.8 million pounds.

Exactly when that reduction will take place is not yet clear, though. The EPA did not set a deadline for the upgrade when it proposed the new permit limit in December.

The reason, according to EPA officials, is because upgrading sewage treatment at the plant is partially intertwined with plans to control massive overflows of sewage-contaminated stormwater into the Anacostia River. The spills stem from antiquated sewer lines that were build before 1900 and serve about a third of the District. The sewer lines combine both sewage and stormwater and send them to Blue Plains for treatment. During rain storms, the system frequently overflows, spilling untreated sewage into the Anacostia River.

In a 2004 court-approved consent decree between the EPA and District of Columbia Water and Sewer Authority, the authority agreed to a 20-year schedule to resolve the overflow problem, which could cost up to $2 billion. It involves collecting and temporarily storing up to 193 million gallons of stormwater and sewage at a time, then sending it to Blue Plains for treatment.

High flows into the plant during rain storms also reduce its ability to remove nitrogen from wastewater, said Jon Capacasa, water division director for EPA Region III. As a result, the upgrade to remove additional nitrogen from the sewage has to be coordinated with plans to resolve the longstanding combined sewer overflow problem. “The two are interrelated,” he said.

Capacasa said the agency will write a compliance schedule to meet the permit limit, with measurable milestones, after negotiations with the plant operators. “It is a complex facility with ongoing construction and several difficult, competing pollution control challenges,” he said.

The EPA plans to have the compliance schedule incorporated into the existing consent decree, which Capacasa said, “has clear advantages in terms of its enforceability and will provide for full public participation at key stages of facility plan development.” The EPA hopes to have a compliance schedule proposed for incorporation into the consent agreement in late February or March.

But the EPA’s decision not to include the compliance schedule with the permit drew fire from some environmentalists. “We really aren’t happy,” Beth McGee, senior scientist with the Chesapeake Bay Foundation, said of the proposed permit limit for the plant. “It was a hollow victory if there is no compliance schedule.”

McGee said she would rather see the compliance schedule be subject to comment with the proposed permit because outside groups have little ability to influence or challenge proposed changes in a consent decree. “They could make them comply in 2020 for all we know,” she said.

Until now, the District of Columbia—which completed upgrades to the plant in the late 1990s that slashed nitrogen discharges by more than 75 percent—has resisted further upgrades. Because of the earlier improvements, the District was the only Bay jurisdiction that met old nitrogen reduction goals set for the year 2000. District officials have said their priority is fixing the costly combined sewer overflow problem, which is contaminating local waterways.

Municipalities in Maryland and Virginia have state funding sources to draw on to help pay for their portions of the upgrade; the District does not.

In January, the Chesapeake Bay Commission, which represents the legislatures of the Maryland, Pennsylvania and Virginia, wrote the Office of Management and Budget asking that $66 million be included in the president’s budget for 2008 to help pay for the upgrades.

The letter stated that “it is the obligation of the federal government to play a major role in funding the necessary upgrades to the Blue Plans facility,” noting that effluent from most federal facilities and stormwater from federal property goes to Blue Plains.

The Blue Plains Wastewater Treatment Plant is not only the largest treatment plant in the Bay watershed, it’s one of the largest in the world. It covers 150 acres and is designed to handle 370 million gallons per day, although it can handle a billion gallons a day during peak flows.

The collection system includes 1,800 miles of sewer lines. It serves customers in the District of Columbia, Montgomery and Prince Georges counties in Maryland and Fairfax and Loudoun counties in Virginia.

In 2005, the plant discharged 5.2 million pounds of nitrogen, according to figures from the EPA’s Bay Program Office. But the exact discharge varies from year to year, depending on temperatures (warm temperatures help biological processes that remove nitrogen), rainfall (which sends more water through the plant, making treatment less efficient) and other variables.

Officials expect that, when the plant is upgraded, it will actually discharge less than 4.7 million pounds of nitrogen most years because engineers design plants to operate well below permit limits.

Additional, though smaller, nitrogen reductions will be realized when the combined sewer overflow problem is fixed.